JPH04336455A - Highly strong lead frame member - Google Patents

Abstract

PURPOSE:To achieve high strength without requiring considerable increase of cold rolling rate in work hardening. CONSTITUTION:At least one of Nb, Zr, Mo or Ta is added, as a solid solution reinforcing element, to a material of lead frame, i.e., an Fe-Ni alloy having low thermal expansion coefficient, which is enhanced in strength through work hardening.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to improvements in lead frame materials used as lead frames for ICs (integrated circuits) and the like.

0002

[Prior Art] Lead frame materials such as ICs are generally made of Fe-Ni alloys with a small coefficient of thermal expansion, such as Fe-42.
Invar, such as Ni alloy, is used, but as ICs become smaller and more highly integrated, it becomes necessary to reduce the thickness of the lead frame material and narrow the width of the leads punched out of the lead frame material. desired. For example, the thickness of the lead frame material, which was conventionally 0.25 mm, will be reduced to about 0.1 to 0.15 mm.

0003

[Problems to be Solved by the Invention] However, when the lead frame material is made thinner or the lead width is made narrower, there is a problem that sufficient strength cannot be obtained. In addition, conventionally, work hardening by cold rolling etc. has been carried out to increase the strength.
) In order to achieve the above, it is necessary to significantly increase the rolling rate, which causes anisotropy and causes problems in subsequent punching, bending, etc.

The present invention has been made against the background of the above circumstances, and its purpose is to provide a material with sufficient strength for practical use without significantly increasing the rolling rate etc. for work hardening. There is a particular thing.

[0005]

[Means for Solving the Problems] In order to achieve the above object, the present invention provides a lead frame material in which an Fe-Ni alloy having a small coefficient of thermal expansion is work-hardened to have high strength. It is characterized in that at least one of Nb, Zr, Mo, and Ta is added as a solid solution strengthening element.

[0006]

[Operation and Effects of the Invention] That is, when Nb, Zr, Mo, or Ta is added to a Fe-Ni alloy, the hardness and tensile strength are improved due to the solid solution strengthening of these elements.
It becomes possible to obtain sufficient strength for practical use as a lead frame material without increasing the rolling rate for work hardening, etc., and this makes it possible to reduce the thickness of the lead frame material and narrow the lead width. This makes it possible to achieve higher density. In addition, since there is no need to increase the rolling rate etc. for work hardening, there is no risk of deterioration in workability due to anisotropy, etc., and punching and bending processes when used as lead frames can be performed well. It has the advantage of being

[0007] Here, as the above-mentioned Fe-Ni alloy, Fe-42Ni alloy and Fe-36
A material containing approximately 40 wt% of Ni, such as a Ni alloy, is preferably used. Additionally, the amounts of Nb, Zr, Mo, and Ta added vary depending on the type of Fe-Ni alloy;
For b and Zr, about 1.5 (wt%) or more, M
o and Ta are preferably about 2.0 (wt%) or more, and at a rolling rate of about 40% for work hardening, the Vickers hardness is 250 or more and the tensile strength is 90 (kgf/mm2).
The above can be achieved. It is also possible to add multiple types of these solid solution strengthening elements, and in that case, the amount of each element added may be less than the above numerical value, for example, Nb and Zr.
When Mo and Ta are added, the total amount is about 1.5 (wt%) or more, and when Mo and Ta are added, the total amount is about 2.5% (wt%) or more.
It is sufficient if it is about 0 (wt%) or more.

[0008]

DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below in detail with reference to the drawings.

FIGS. 1 to 3 show Fe-42Ni with Nb and Z
r, Mo, and Ta were 1.0 (wt%) and 2.0 (
2 is a diagram showing the Vickers hardness, tensile strength, and 0.2% yield strength of a lead frame material prototyped with the addition of 3.0 (wt%). Such a lead frame material is manufactured according to FIG.
It is hot-rolled at about ~1200°C to form a plate material with a thickness of about 3-5 mm. Thereafter, cold rolling and vacuum annealing were repeated three times to reduce the plate thickness to 0.25 mm. Vacuum annealing was performed for the purpose of removing anisotropy and internal stress generated by cold rolling, and was slowly cooled by holding at 1000° C. for 2 minutes. Finally, the rolling ratio {(T1 − T2
)/T1 }×100 of 40% to work harden the material, and obtain a lead frame material having a target thickness of 0.15 mm.

[0010] In Figs. 1 to 3, the "x" mark indicates the value when lead frame material was manufactured in the same manner as above from Fe-42Ni that does not contain the above-mentioned additive elements.
Lead frame materials manufactured by adding , Mo, or Ta have improved Vickers hardness, tensile strength, and 0.2% yield strength due to solid solution strengthening by these elements.
It can be seen that a higher value can be obtained compared to 42Ni. especially,
About 1.5 (wt%) or more for Nb and Zr,
If about 2.0 (wt%) or more of Mo and Ta are added, the Vickers hardness will be about 250 or more and the tensile strength will be about 90 (kgf/mm2) or more.
Even with a plate thickness of 0.15 mm, sufficient strength for practical use as a lead frame material can be obtained.

In addition, since the rolling rate for work hardening is 40%, which is not so large, there is no risk of deterioration of workability due to anisotropy, etc., and punching and bending work when used as a lead frame can be performed well. It will be done.

[0012] In the above example, Nb,
Zr, Mo, and Ta were 1.0 (wt%) and 2.0, respectively.
(wt%), 3.0 (wt%) has been described, but it goes without saying that the amounts added can be changed as appropriate. However, in order not to impair the basic properties of Fe-42Ni, it is desirable to limit the amount of these additions to about 5 (wt%) or less.

Further, in the above example, the rolling rate for work hardening was 40%, but the rolling rate may be changed within a range that does not cause deterioration of workability due to anisotropy or the like. The thickness of the final lead frame material is not limited to 0.15 mm either.

[0014] Furthermore, the strength of the lead frame material can be further increased by adding precipitation hardening elements in addition to the above solid solution strengthening elements.

Although no other examples are given, the present invention can be implemented with various modifications and improvements based on the knowledge of those skilled in the art.

[Brief explanation of drawings]

FIG. 1 is a diagram showing the Vickers hardness of multiple types of lead frame materials according to the present invention.

FIG. 2 is a diagram showing the tensile strength of multiple types of lead frame materials according to the present invention.

FIG. 3: Zero of multiple types of lead frame materials according to the present invention.
．． It is a figure showing 2% yield strength.

4 is a diagram showing a manufacturing procedure for the lead frame material shown in FIGS. 1 to 3. FIG.

Claims (1)

[Claims] 1. A lead frame material in which a Fe-Ni alloy with a small coefficient of thermal expansion is work-hardened to increase its strength, wherein the Fe-Ni alloy is solid solution strengthened with at least one of Nb, Zr, Mo, and Ta. A high-strength lead frame material characterized by the addition of elements.